A total of 89 patients, (>18 years), with symptoms of chronic prostatitis and inflammatory findings as well as the presence of Chlamydia trachomatis confirmed by DNA/RNA DIGENE hybridization method and/or by isolation, McCoy culture and Lugol stain in expressed prostatic secretion or in voided bladder urine collected immediately after prostatic massage, were examined. The patients were randomized to receive a total of 4.5 g of azithromycin for 3 weeks, given as a 3-day therapy of 1x500 mg weekly or ciprofloxacin 500 mg b.i.d. for 20 days. Patients' sexual partners were treated at the same time. Clinical and bacteriological efficacy were evaluated 4-6 weeks after the end of therapy. Significantly higher eradication (36/45: 17/44; P=0.0002) and a significantly higher clinical cure (31/45: 15/44; P=0.0021) were achieved in the group of patients treated with azithromycin than in the ciprofloxacin group.